The combustion system of a gas turbine contains the hot gasses and flame produced during the combustion process, and channels the hot gas to the turbine section of the engine. An industrial gas turbine engine commonly has several individual combustor assemblies arranged in a circular array about the engine shaft. A respective circular array of transition ducts, also known as transition pieces, connects the outflow of each combustor to the inlet of the turbine section. Each transition piece is a tubular structure that channels combustion gas between a combustor and the first row of stationary vanes or rotating blades of the turbine section, whichever comes first in a given engine design. U.S. Pat. No. 7,721,547 illustrates examples of such various engine designs.
To increase gas turbine engine efficiency, the temperature of the working gas in gas turbine designs is being increased. This requires increasing the compressor pressure ratio, which increases the temperature of the compressed air feeding the combustor. This same compressed air is commonly used both for combustion and for cooling the combustor and transition piece. However, the higher-temperature compressed air of modern gas turbine engines poses a challenge for materials of the combustion system, including the shell that encloses the combustion system. Either higher-priced materials or additional shell cooling, which penalizes cycle efficiency, is required.